Apocalypse Arizona?

Published August 1, 2000

The Environmental Protection Agency has released its “State and Local Climate Change Outreach Kit”–which its cover calls a “one-stop shop . . . packed with useful materials” to help you “reach out on climate change.”

Curious about the fate of my immediate surroundings, I downloaded the four-page brochure entitled, “Climate Change And Arizona.” (There are brochures for every state.)

“Apocalypse Arizona” is more like it.

Somewhere in the (misinformed) hysteria about extreme hot days, winter storms, asthma, giardia, crytosporidia, and hantavirus pulmonary syndrome is a statement that, under warmer summer temperatures, “livestock tend to gain less weight and pasture yields decline, limiting forage.”

Of course, we at Greening Up beg to differ. Time and again, we have demonstrated how grasses throughout the world increase biomass with elevated CO2, becoming more water-use efficient and more resistant to drought and other stressors. Somehow, EPA failed to note the countless scientific studies on this topic–including two recent articles on the fate of the desert when CO2 increases.

Yoder and colleagues begin the first of these fairly predictably: “Hot deserts, such as the Mojave Desert in southwestern North America, are predicted to be among the most sensitive ecosystems to rising atmospheric CO2 concentration.” True enough. But here’s a twist. They immediately note that the resulting decreased plant circulation will increase water-use efficiency in dryland plants:

“Increased water-use efficiency is especially important in arid ecosystems, and models that incorporate effects of elevated CO2 on water-use efficiency predict that deserts will have among the largest relative increase in net primary production.”

Changes, all right–but increased biomass is hardly a bad thing.

The team found grass seed grown at atmospheric CO2 levels of 360 ppm (the natural level) and 1,000 ppm (the standard commercial greenhouse level) caused two varieties of grass to increase their overall dry weight by 40 percent and 19 percent; the third variety decreased its biomass production. For all three varieties, soil moisture went up with elevated CO2, indicating the plants were using less water.

In a second study–especially noteworthy because it spanned two years–Sgherri and colleagues grew alfalfa in open-top chambers with atmospheric CO2 at 340 ppm and 600 ppm. During the second year, the plants were subjected to drought and–you guessed it–“CO2-enriched plants were less affected by drought.” They concluded:

“Alfalfa plants responded to a long-term CO2 enrichment with the highest water-use efficiency, decreased photorespiration, and increased antioxidant abilities. . . . As a consequence, an interaction between CO2 and drought increased the alfalfa plants’ capacity to deal with oxidative stress as compared to plants grown at ambient CO2.”

These recently published findings are clearly at odds with what EPA would have us believe. Protecting the environment, EPA’s mission, would seem to include helping plants grow greener and better and cope with stressors like drought. But a campaign of misinformation does just the opposite.

Robert C. Balling Jr., Ph.D. is director of the Laboratory of Climatology at Arizona State University and coauthor of The Satanic Gases.


Sgherri, C.L.M., et al., 2000. Interaction between drought and elevated CO2 in the response of alfalfa plants to oxidative stress. Journal of Plant Physiology, 156, 360-366.

Yoder, C.K., et al., 2000. Root growth and function of three Mojave Desert grasses in response to elevated atmospheric CO2 concentration. New Phytologist, 145, 245-256.